Galaxies come in many shapes and sizes. The Milky Way, for example, is a spiral galaxy because of the way that stars, dust, and gas spiral out from the center of the galaxy.

But spiral galaxies like ours are surprisingly rare in our galactic neighborhood, and for years, astronomers have wondered why since the 1960s.

Now, they may finally have an answer, according to a new study published in the peer-reviewed journal Nature Astronomy earlier this month.

A turbulent past

Using a supercomputer, researchers turned back the clock to approximately 13.8 billion years ago when our galaxy and those around it were just starting to form.

The researchers simulated the evolution of our galactic neighborhood to see what may have happened over billions of years to make spiral galaxies so rare in our corner of the cosmos.

They found evidence of a turbulent past. The simulation showed that galaxies in dense clusters, like the one our Milky Way calls home, experienced frequent collisions and mergers.

When galaxies collide

When galaxies merge, they can form a whole new type of galaxy. For example, when two spiral galaxies collide, it's thought to create what's called an elliptical galaxy.

That's what both observations of our nearby universe and the simulations showed: Our galactic neighborhood has plenty of elliptical galaxies but very few spiral galaxies, suggesting that our Milky Way somehow survived amidst a chaotic scenario of galactic bumper cars over the age of the universe.

"Our simulation reveals the intimate details of the formation of galaxies such as the transformation of spirals into ellipticals through galaxy mergers," said co-author Carlos Frenk with the Institute for Computational Cosmology at Durham University in a statement.

This article was originally published by Business Insider.

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